This invention relates to compositions and methods for sealing pits and fissures in tooth enamel surfaces. More particularly, it relates to visible light curable sealant compositions.
Dental surface imperfections such as pits and fissures can harbor microorganisms which, on proliferation, cause the formation of caries. These imperfections are particularly troublesome in deciduous teeth and have historically been the source of great discomfort for children. Ordinary dental hygienic methods such as toothbrushing and professional prophylaxis are quite ineffective against these imperfections since such pits and fissures are typically too narrow to permit contact by bristles or prophylaxis instruments.
In order to avoid the problems caused by microorganism growth and adhesion in dental pits and fissures, the general practice now is to seal these imperfections in order to eliminate the sites for proliferation of such microorganisms. The generally used pit and fissure sealants contain polymerizable resins such as the polymerizable acrylic resin system for use in dentistry described in U.S. Pat. No. 3,066,112. These polymerizable resins are used without filler in order to provide a sealant of sufficiently low viscosity to flow into the pits and fissures so as to assure complete sealing and good adhesion to the surrounding tooth surface.
The polymereizable resin systems usable as pit and fissure sealants can include many resins within the wide range of acrylic monomers and the diluent monomers currently used in restorative dentistry. The resinous compositions also include the necessary polymerization initiators and accelerators and the optional (but preferable) inhibitors and ultraviolet absorbers.
Although excellent sealing and adhesion can be obtained by the use of various polymerizable acrylic resin systems, such resin systems are generally either transparent or translucent and consequently it is difficult for the dentist to discern whether the sealant has been properly placed. Thus, it is often quite difficult to determine whether the pits and fissures are completely sealed, whether some pits and fissures have remained unsealed or, conversely, whether too much sealant has been used. Furthermore, subsequent examinations by the dentist to determine whether sealant has become worn or dislodged are rendered difficult or uncertain because of the difficulty in ascertaining the presence or absence of such transparent or translucent sealants.
The addition of a pigment to polymerizable resin sealant composition provides an easily discernable composition which avoids the problems encountered by transparent or translucent dental sealants. However, such pigments tend to settle out of the sealant composition upon standing. Therefore, the sealant composition containing pigment must be stirred thoroughly prior to each use or, alternatively, the pigment cannot be added until the sealant composition is ready for use. In U.S. Pat. No. 4,150,012, there is disclosed a two-part pit and fissure sealant composition containing an opaquing filler material and a hydrophobic suspending agent.
Despite recent improvements as far as opacity is concerned, improvements in the physical characteristics of the sealants themselves are desirable. In particular, it is desirable to develop suitable readily discernable pit and fissure sealants which exhibit improved surface hardness versus depth of cure and ultimate degree of polymerization. In addition, it is desirable to provide sealants which exhibit improved diametral tensile strength sufficient to avoid premature edgewise chip fracture and which exhibit improved retention. In addition, sealants exhibiting these properties coupled with the convenience of a visible light curing technique would be particularly desirable.